The present invention is related to storage media. More particularly, the present invention is related to systems and methods for identifying defective regions on a storage medium.
A typical storage medium includes a number of storage locations where data may be stored. Data is written to the medium within areas designated for user data by positioning a read/write head assembly over the medium at a particular location, and subsequently passing a modulated electric current through the head assembly such that a corresponding magnetic flux pattern is induced in the storage medium. To retrieve the stored data, the head assembly is positioned over a track containing the desired information and advanced until it is over the desired data. In this position, the previously stored magnetic flux pattern operates to induce a current in the head assembly. This induced current may then be converted to represent the originally recorded data.
The storage locations on the storage medium are typically arranged as a serial pattern along concentric circles known as tracks. FIG. 1 shows a storage medium 100 with two exemplary tracks 150,155 indicated as dashed lines and written respective distances from an outer perimeter 140. The tracks are segregated by servo data written within wedges 160, 165. These wedges include data and supporting bit patterns that are used for control and synchronization of the head assembly over a desired storage location on storage medium 100. In particular, such wedges traditionally include a preamble pattern 152 followed by a single sector address mark (SAM) 154 as shown by element 110. The SAM 154 is followed by a Gray code 156, and the Gray code 156 is followed by burst information 158. It should be noted that while two tracks and two wedges are shown, hundreds of each would typically be included on a given storage medium. Further, it should be noted that a sector may have two or more bursts.
Manufacturing the storage medium includes performing a variety of steps any of which can result in a defective region on the storage medium. Further, defective regions may develop over the time that the storage medium is used. Writing data to a defective region can result in the loss of such data. To avoid this, some approaches have been developed to identify defective regions as unusable. This works reasonably well, but does not identify regions that become defective over time and does not always identify all defective regions. In such cases, such an approach is not effective.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for identifying defective regions on a storage medium.